In conventional gear cutting machines, principally, gear shapers, a cutter spindle motor causes a tool to perform a stroke operation (linear reciprocal movement) in a vertical direction of the tool (in a spindle direction). In addition, in synchronism with this cutter spindle motor, a cam mechanism causes the tool to move toward or away from a gear to be cut in a direction orthogonal to the cutter spindle, that is, to perform a relieving operation.
FIG. 13 is a schematic view for explaining a cam mechanism of a conventional gear cutting machine. As shown in this figure, the conventional gear cutting machine has a cam 101 linked to a cutter spindle motor with a gear train (the illustration is omitted) and configured to rotate mechanically and synchronously. Together with the rotation of the cam 101, a cam lever 102 moves, and the movement of the cam lever 102 via a four-bar link mechanism 104 provided to the cam lever 102 causes a cutter 105 to perform the relieving operation.
FIG. 14 is a schematic diagram for explaining a path of the cutter in the conventional gear cutting machine, and the solid arrow in this figure indicates the path of the cutter. As shown in this figure, the cutter 105 in the conventional gear cutting machine performs machining in a cutting step (top dead center→bottom dead center), and performs a relieving operation in a returning step (bottom dead center top dead center) so that the cutter 105 can avoid interfering with a gear 21 to be cut in the returning step.